Method of sealing display cathodes in a glass envelope

ABSTRACT

A method of sealing display cathodes in a glass envelope wherein the cathodes having lead wires attached thereto are inserted into a glass envelope having an insertion port. A heatproof insulating stem is then inserted into the glass envelope to a position based inwardly from the insertion port. The stem has apertures which receive the lead wires of the cathodes so that they lead out to the insertion port side of the envelope. Fusion glass is then packed in the space between the stem and the part of the glass envelope about the insertion port and in the spaces formed between the lead wires and the apertures. The fusion glass is then heated by an infrared radiation source to simultaneously fuse and integrally bond the stem with both the lead wires and glass envelope.

United States Patent 1 1 3,632,324

7 Inventors Kiyoshi Sasaki; 3,217,088 1 1/1965 Steierman 65/40 x Satoshi W n both of ky Jap n 3,352,655 1 1/1967 Barch 65/28 [21] pp 60 3,332,790 7/1967 Penberthy 106/52 [22] F1led May 31, 1968 3,434,818 3/1969 Chauvin 65/1 Patented Jan. 4, 1972 2,248,644 7/1941 Reger et al... 65/43 Asslgnee Okaya Denki Sangyo Kabushiki Kaisha 3,250,938 5/1966 Frouws et a1. 313/1095 [32] Priority Primary ExaminerS. Leon Bashore [33] Japan Assistant ExaminerSaul R. Friedman [3 l] 2/51361 Attorney-Hill, Sherman, Meroni, Gross & Simpson 54 METHOD OF SEALING DISPLAY CATHODES IN A ABSTRACT A i a g'ass GLASS ENVELOPE envelope wherem the cathodes havlng lead wrres attached 9 Ciaims, 5 Drawing Figs. thereto are inserted into a glass envelope having an insertion port. A heatproof insulating stem is then inserted into the glass {52] US. Cl 65/43, envelo e to a osition based inwardly from the insertion port. 65/59 The stem has apertures which receive the lead wires of the [51 Int. Cl C03c 27/04 cathodes that they lead out to the insertion port side Of thC [50] Field of Search /40, 43, envelope, Fusion glass is then packed in the space between [116 313/1095 stem and the part of the glass envelope about the insertion port and in the spaces formed between the lead wires and the [56] References (med apertures. The fusion glass is then heated by an infrared radia- UNITED STATES PATENTS tion source to simultaneously fuse and integrally bond the 2,749,668 6/1956 Chafiotte et al. 65/43 stem with both the lead wires and glass envelope.

3,120,433 2/1964 Van Z88 65/43 METHOD OF SEALING DISPLAY CATHODES IN A GLASS ENVELOPE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a display device, and more particularly to a display device adapted to display numerals and/or characters by means of electrodes disposed in predetermined relationship and a method of making the same.

2. Description of the Prior Art Conventional types of display devices present problems such as complexity in the provision of a plurality of display cathodes, possibilities of bad insulation between the display cathodes and bad contact thereof with their lead wires. Further, sputtering of the display cathodes blurs the glass tube envelope and also introduces bad insulation between the cathodes.

In addition, the prior art encounters difficulties in the fabrication of such display devices as it requires complicated operations for sealing up display cathodes within the glass envelope and involves a considerable amount of time therefor and allows nonuniformity in the sealing of the glass envelope.

SUMMARY OF THE INVENTION This invention is to provide an electronic display device which is designed such that display cathodes are held in position in completely electrically insulated condition, the envelope is not blurred by sputtering of the cathodes and lead wires of the cathodes are attached to the envelope while being electrically insulated from one another and a method of making such a display device which allows base in manufacturing processes.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an enlarged perspective view, partly cut away, illustrating, by way of example, the principal part of the display device produced according to this invention;

FIG. 2 is a perspective view illustrating one example of the display device of this invention;

FIG. 3 is a schematic diagram for explaining one example of a method for sealing the glass envelope of the display device;

FIG. 4 is a crosssectional view of the sealed portion of the glass envelope; and

FIG. 5 is a longitudinalsectional view of the glass envelope after sealed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to the drawings the present invention will hereinafter be described in detail, by way of example.

In FIG. 1 reference numeral 1 indicates a base plate made of an insulating material, for example, ceramic, which has a recess 2 formed in, for instance, the upper face in the drawing. A plurality of grooves 3 of a predetermined shape, for example, straight configuration in the illustrated example, are provided in the bottom of the recess 2 and cathodes 4 formed of nickel or the like are placed in the grooves 3 in a manner not to project out therefrom. While, a meshlike anode 5 common to the cathodes 4 is stretched over the recess 2 in opposing but spaced relation to the cathodes 4. In the illustrated example the anode 5 is a mesh formed of a conductive material such as iron or the like and is stretched between a pair of supports 5 of iron or the like, which are, in turn, attached to the edges 2' of the recess 2 of the baseplate l. The anode 5 may be a thin iron plate whose intermediate portion is formed to be meshlike by means of, for example, etching.

A plurality of grooves 6, seven grooves in the present example, corresponding to the grooves 3 and consequently the cathodes 4 are formed in the ceramic base plate 1 on the side of its underside in its lengthwise direction, as depicted in FIG. 1. Further, bores 6' are respectively formed in the base plate 1 through which each groove 3 is contiguous to each groove 6, and lead wires 7 are respectively connected to the cathodes 4,

located in the grooves 3, through the grooves 6 and the bores 6'. The cathodes 4 may be formed by bending one end portion of the lead wires 7. The formation of the cathodes 4 may take place by means of vapor deposition or electrode position, by which the cathodes 4 can be formed in a substantially semicylindrical shape to cause a decrease in a discharge supporting voltage due to the so called follower effect. Reference numeral 8 designates a lead wire of the anode 5.

The electrode assembly of such an arrangement as described above is housed in an airtight envelope, as shown in FIG. 2. That is, the electrode assembly is mounted on a substantially disclike stem 9 formed of an insulating material such as ceramic or the like and is then sealed up in a transparent glass envelope 10. In order to provide enhanced airtightness of the envelope 10, the stem 9 is sealed up at the open end portion of the glass envelope 10 with, for example, glass 10'. The envelope 10 is filled with a predetermined gas, for example, neon Ne, argon A or the like.

With such an arrangement, the application of a predetermined voltage to the cathodes 4 and the anode 5 through their lead wires 7 and 8 leads to the production of glow discharge of the cathodes 4 to display a numeral, character or the like (a numeral 8" in the illustrated example) of a predetermined shape.

It is preferred to lay down a black paint on the surface and sides of the ceramic base plate 1 so as to provide clear display, or the use of a black base plate is more effective for the purpose.

In the device of this invention the cathodes 4 are disposed in the grooves 3 formed in the base plate 1 in a manner not to project out from the surface thereof and this ensures insulation between the cathodes to eliminate bad insulation therebetween experienced in the past and removal of bad contact between the lead wires and the cathodes. In addition, the cathodes 4 are merely placed in the grooves 3 and hence this allows ease in the manufacturing operations, and the base plate 1 can be utilized for supporting the cathodes 4.

Further, sputtered cathode material is deposited only in the grooves 3 and is hardly deposited on the surface of the base plate 1, which eliminates the possibility of bad insulation between the cathodes and blurring of the surface of the base plate due to sputtering of the cathodes, encountered in the prior art. Since the lead wires 7 of the cathodes 4 are led out through the bores 6' and the grooves 6, they can be held in position well insulated from one another. This completely removes the possibility of discharge between the lead wires and contact troubles thereof.

In accordance with this invention the insulation between the cathodes and between the lead wires is excellent, so that even if the ceramic base plate 1 is miniaturized, there is no possibility of causing bad insulation, and this permits of considerable miniaturization of the entire structure. In addition, since the device is simple in construction, it is inexpensive, easy to manufacture requiring less manufacturing operations and hence is suitable for mass production. Even if the cathodes 4 are embedded in the grooves 3, their glow discharge swells toward the anode, so that no troubles are introduced in the display.

Although the present invention has been described in connection with a case of displaying the numeral 8 by glow discharge, it is to be understood that various numerals, characters and the like can be displayed by various modifications of the shape and relative position of the grooves 3. It is also possible that various numerals, characters and the like can be displayed by one display device by applying input signals to selected electrodes disposed in grooves provided in the form of a matrix. Further, display of numerals, letters and the like can be efi'ected not only by glow discharge but also by phosphor discharge with phosphor material deposited on the surface of the cathodes. The foregoing example is intended as being illustrative and not as limiting this invention specifically thereto, and various modifications may be efi'ected when needed.

Referring now to FIGS. 3 to 5, detailed description will hereinafter be given of one example of a method for sealing the electrode assembly in the glass envelope or the like. For convenience of description, the following description will be made in connection with the case of displaying a numeral "2.

As illustrated in FIG. 3, an electrode assembly including display cathodes 102, a lead wire 103 and so on is placed in a glass envelope 101 having a gas exhaust pipe 101a in such a manner that a display portion 102 is located on the side of the exhaust pipe 101a. In this case, an insulating member 106 of, for example, mica is disposed in the envelope 101 for positioning of the display portion 102 of the electrode assembly. Then, a stem 104 formed of an insulating material such as ceramic or the like is inserted into the envelope 101, in which case the stem 104 has a plurality of apertures 104a formed therethrough at the center and the lead wire 103 is led outside of the envelope 101 through one of the apertures 1040.

Further, infrared ray absorbing glass powder or piece or its mixture 105 with black carbon and/or chrome oxide powder having lightabsorbing property is packed into the envelope 101 between the free end face of the stem 104 and the open end portion of the envelope 101 and between an aperture 104a and the lead wire 103 therein. The black carbon, chrome oxide or like powder mixed in the infrared ray absorbing glass absorbs light and hence increases light absorbing efficiency, since it prevents transmission of light as in the case of the infrared ray absorbing glass only.

In FIG. 3 reference numeral 107 designates generally one example of an infrared radiation source for sealing the glass envelope, which employs an infrared ray lamp 108 such as a quartz iodine lamp and an elliptic mirror or reflector such as indicated by 109. As is well known, the elliptic mirror 109 has a curved face formed by cutting off vertically an elliptic plane formed by turning an ellipse about a line joining its two focuses relative to this line, and the curved interior surface of the elliptic plane is plated with, for example, gold. The aforementioned lamp 108 is disposed at one focus, for instance, near the elliptic mirror 109 and the frit glass 105 is placed near the other focus remote from the mirror 109. With such an arrangement, the light of the lamp 108 is reflected by the mirror 109 to be directed to the other focus, so that the portion including the frit glass 105 is subjected to strong light (heat). That is, the frit glass 105 is exposed irradiation of strong infrared ray and is thereby fused to easily seal the envelope.

A description will be given in connection with one example of numerical values in the abovedescribed sealing method.

The softening point of the infrared ray absorbing glass 105 is 625 :5 C. and its coefficient of expansion is (89.5 11.5) X l"". On the other hand, the softening point of glass for usual electronic tube envelopes is 684:C. and its coefficient of expansion is approximately (98i2) X and further the coefficient of expansion of ceramic is approximately 9l.5Xl0 at a temperature ranging from to 400C. It will be apparent from the foregoing that the softening point of the infrared ray glass is appreciably lower than that of the glass of the envelope. Accordingly, taking advantage of the difference in the softening point, the infrared ray absorbing glass is fully exposed to irradiation by infrared ray to cause it to be softened and fused to the stem 104 and envelope 101 before softening of the envelope.

In this case, the coefficient of expansion of the infrared ray absorbing glass is substantially equal to that of the glass envelope, and the coefficient of expansion of ceramic is also nearly equal thereto. Consequently, where these three materials are fused together, they do not introduce distortion and can be well fused. One example of numerical values of a cold cathode discharge tube used under such conditions is such that the thickness of the envelope is 0.5 to 0.7 mm., its diameter is l0 mm., the thickness of ceramic is 3 mm. and the temperature of infrared irradiation is 1,200 to 1,600 C. at maximum. The fusing operation can be effected with suitable adjustment of this temperature. Where the thickness of the infrared ray absorbing glass is 2.5 to 3.0 mm., the fusing time is as short as about 15 seconds and the resulting envelopes are extremely uniform in thickness without producing distortion, and consequently the yield is very high. In this manner, the indicator tube envelope can be positively sealed with the cathodes held in position.

FIG. 5 is a crosssectional view of a cold cathode discharge tube thus produced according to this invention, and the outer end of the fused glass is a little swelled out as indicated at 1054. After sealing the envelope air in the envelope is evacuated through the exhaust pipe 1010 on the opposite side from the sealed portion or neon, argon gas or the like is sealed in the envelope through the exhaust pipe 101a, after which the exhaust pipe 101:: is burned off, thus producing a desired discharge tube.

As has been described in the foregoing, the present invention improves the complicated conventional method to allow ease in the fusing operation, shorten the time for sealing the elements of the display tube in the envelope and hence enhance the operating efficiency. In addition, the glass envelope, the ceramic stern and the frit glass containing the infrared ray absorbing glass for sealing them are sufficiently fused together substantially without any distortion. Accordingly, there is no possibility that the display electrodes get out of position during the sealing operation of the envelope, and the yield is very high. That is, the method of the present invention is of particular utility when employed in the sealing of cold cathode discharge tubes of the type described above.

It will be apparent that many modifications and variations may be effected without departing from the scope of the novel concepts of this invention.

We claim as our invention:

1. A method of sealing a glass envelope for an electronic tube comprising the steps of: inserting display cathodes into a glass envelope having an exhaust port at one end and an inserting port at the other end from the insertion port side, each display cathode having already attached thereto a leadwire, inserting a heatproof insulating stem into the glass envelope from the insertion port side to a position based inwardly from the insertion port, the heatproof insulating stern having bored therethrough apertures for receiving the display cathodes; leading out the lead wires through the apertures of the heatproof insulating stem to the insertion port side of the glass envelope; packing fusion glass of low melting point in the space formed between the heatproof insulating stem and the part of the glass envelope about the insertion port thereof and in spaces formed between the lead wires and the apertures of the stern; and heating the fusion glass with an infrared ray from the free end surface of the fusion glass, said infrared ray being emanated from an infrared radiation source positioned in right opposed and spaced relation to the free end of the fusion glass packed in the envelope, to simultaneously fuse and integrally bond the heatproof insulating stem with both the glass envelope and the lead wires.

2. A method of sealing a glass envelope for electronic tubes as claimed in claim 1 wherein the fusion glass is infrared ray absorbing glass.

3. A method of sealing a glass envelope for electronic tubes as claimed in claim 1 wherein the fusion glass is a mixture of infrared ray absorbing glass with black carbon.

4. A method of sealing a glass envelope for electronic tubes as claimed in claim 1 wherein the fusion glass is a mixture of infrared ray absorbing glass with chrome oxide powder.

5. A method of sealing a glass envelope for electronic tubes as claimed in claim 1 wherein the fusion glass is a mixture of infrared ray absorbing glass with black carbon and chrome oxide powder.

6. A method of sealing a glass envelope for electronic tubes as claimed in claim 1 wherein the heatproof insulating stem is made of ceramic.

7. A method of sealing a glass envelope for electronic tubes as claimed in claim 1 wherein the fusion glass is in the form of powder.

8. A method of sealing a glass envelope for electronic tubes as claimed in claim 1 wherein the fusion glass is in the form of a piece.

9. A method of sealing a glass envelope for electronic tubes as claimed in claim 1 wherein the infrared radiation source 5 consists of an elliptic mirror and an infrared lamp disposed at one of the focuses of the elliptic mirror. 

2. A method of sealing a glass envelope for electronic tubes as claimed in claim 1 wherein the fusion glass is infrared ray absorbing glass.
 3. A method of sealing a glass envelope for electronic tubes as claimed in claim 1 wherein the fusion glass is a mixture of infrared ray absorbing glass with black carbon.
 4. A method of sealing a glass envelope for electronic tubes as claimed in claim 1 wherein the fusion glass is a mixture of infrared ray absorbing glass with chrome oxide powder.
 5. A method of sealing a glass envelope for electronic tubes as claimed in claim 1 wherein the fusion glass is a mixture of infrared ray absorbing glass with black carbon and chrome oxide powder.
 6. A method of sealing a glass envelope for electronic tubes as claimed in claim 1 wherein the heatproof insulating stem is made of ceramic.
 7. A method of sealing a glass envelope for electronic tubes as claimed in claim 1 wherein the fusion glass is in the form of powder.
 8. A method of sealing a glass envelope for electronic tubes as claimed in claim 1 wherein the fusion glass is in the form of a piece.
 9. A method of sealing a glass envelope for electronic tubes as claimed in claim 1 wherein the infrared radiation source consists of an elliptic mirror and an infrared lamp disposed at one of the focuses of the elliptic mirror. 